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Trial Results Show Promise for Strep Vaccine

Aug 10, 2004

Preliminary results from a trial for a streptococcal vaccine indicate the vaccine appears likely to offer protection against streptococcal infections, according to a study in the August 11, 2004 issue of the Journal of the American Medical Association (JAMA).

Efforts to develop a vaccine to prevent group A streptococcal (a type of bacteria that commonly causes illness) infections have been ongoing for more than 70 years, according to background information in the article. Recent advances have allowed previous obstacles associated with group A streptococcal vaccine development to be overcome. Group A streptococcal infections and their sequelae represent a global health problem.

Karen L. Kotloff, MD, of the University of Maryland School of Medicine in Baltimore, and colleagues report on a preliminary study evaluating the safety and immune reactivity of a group A streptococcal vaccine in healthy volunteers. The phase 1 vaccine trial included 28 adult volunteers aged 18 to 50 years recruited from the metropolitan area of Baltimore between October 1999 and February 2003. Each volunteer received three spaced intramuscular injections of either 50 micrograms (n=8), 100 micrograms (n=10), or 200 micrograms (n=10) of group A streptococcal vaccine formulated with aluminum hydroxide into the deltoid muscle of alternating arms.

Our findings, albeit in a small number of participants, suggest that in the full dose range tested, the vaccine appears safe and well tolerated and does not evoke antibodies that cross-react with human tissue. We have identified a dose (200 micrograms) and schedule (0, 28, and 112 days) that appears to be capable of inducing immune responses that are likely to confer protection against multiple group A streptococcal M types.

Reference: JAMA. 2004;292:709-715.

In an accompanying editorial, Michael E. Pichichero, MD, of the University of Rochester Medical Center, Rochester, N.Y., writes that the challenges for successful development of group A streptococcal vaccines are substantial.

Very stringent and early studies will lengthen the development process. Uncertainties about targeted immunologic parameters will complicate analysis. Most likely the proposed safety assessment will continue in adults and eventually will progress in phase 2 studies in children. Double-blind, placebo-controlled, stepwise evaluations in cohorts of children with declining age ranges should be anticipated. There will be a need to conduct large prelicensure trials involving 10,000 to 60,000 participants to provide assurance that rare adverse events are not associated with vaccination, particularly with M type vaccines that have demonstrated adverse events in the past. Safety concerns regarding cross-reaction with human tissues necessitates caution, Pichichero concludes.